Electrodeposition of zinc from pyrophosphate solutions



United States Patent Ofitice 3,296,104 ELECTRODEPOSITION F ZINC FROM PYROPHOSPHATE SOLUTIONS Frederick W. Eppensteiner, Woodbridge, NJ., assignor to Hanson-Van Winkle-Munning Company No Drawing. Filed Oct. 29, 1963, Ser. No. 319,666 15 Claims. (Cl. 20455) This invention relates to the electrodeposition of bright zinc in an alkaline pyrophosphate bath containing an improved brightener composition. The invention is based on the discovery that certain organic compounds when incorporated in an alkaline pyrophosphate zinc bath in combination with various carbonyl compounds of the aldehyde and ketone types are capable of promoting the formation of excellent bright and uniformly smooth electrodeposits of zinc over a wide current density range. Moreover, the additives of this invention greatly improve the throwing power of the zinc pyrophosphate plating solution making it particularly suitable for barrel plating.

Alkaline solutions containing complex compounds of Zinc and alkali metal pyrophosphates have been proposed as a replacement for the cyanide bath in electrodeposition of bright zinc, thereby eliminating the troublesome and costly disposal problem associated with the use of cyanide baths. Electrodeposition of zinc using the pyrophosphate bath, however, shows poor low current density coverage, lack of brightness and uniformity of the deposit. Attempts to overcome the deficiency of the bath by adding a few comparatively expensive additives such as ortho-hydroxy-meta-methoxybenzaldehyde, vanillin and its phenol sulfonate condensation product have met with only partial success and pyrophosphate zinc plating baths containing these aldehydes have not attained commercial acceptance. Similarly, I have found some other carbonyl compounds of aldehyde and ketone types have some beneficial effect on the pyrophosphate bath, but they also fail to provide an acceptable bright and uniformly smooth electrodeposit of zinc with good low current density coverage.

I have discovered that a small amount of an organic compound, hereafter referred to as a carrier, selected from the group consisting of (a) his [sulfonaphthyl] methane; (b) naphthalene derivatives that contain substituents selected from the group consisting of sulfonic acids and their alkali metal salts, hydroxyl, amino, and imino radicals; (c) benzene derivatives containing the substituents selected from the group consisting of sulfonic acids and their salts with alkali metal and ammonium, alkyl and imino radicals, and (d) allyl sulfonic acid and its salts with alkali metals, when incorporated into a pyrophosphate zinc plating bath in combination with a carbonyl compound of the aldehyde and the ketone types will increase greatly the brightness and the uniformity of the zinc deposit. The low current density coverage of the bath also is improved, and the resultant electrodeposit of zinc shows a reduction in roughness.

According to this invention a preferred process for producing bright zinc deposits comprises electrodepositing zinc from an aqueous alkaline pyrophosphate solution containing at least one zinc salt in which there is dissolved from about 0.5 to about 5.0 grams per liter of a carrier selected from the group previously stated, and from about 0.025 to about 0.2 gram per liter of a carbonyl compound selected from the group consisting of aldehydes and. ketones.

While the specific carriers of this invention may be used successfully at any concentration within the broad range stated above, it is generally preferable to employ them in a concentration from about 0.9 to about 1.6 grams per liter. Also it is preferred to employ the carbonyl compound at a concentration in the range from about 0.05 to about 0.1 gram per liter. I have found that the maximum brightness of the deposit is not obtained when the concentration of the carbonyl compound is too low. A high concentration of carbonyl compound, on the other hand, decreases the low current density coverage.

No specific procedure is required in adding the carrier to the plating bath. For the carbonyl compound, it is often most convenient to incorporate it in the bath in the form of dilute aqueous solution. For additives having higher carbonyl concentrations, basic aqueous solutions containing alkali metal hydroxide may be used. The short shelf life of this solution, however, requires that it be freshly prepared. For a solution having longer shelf life, the carbonyl compounds may be dissolved in the form of an aqueous-alcoholic solution.

Table I sets forth examples of the carriersthat have been used successfully in the process of this invention.

TABLE I Any of the carbonyl compounds of the aldehydes and ketone types which cooperate efiFectively with the carriers of this invention may be used in combination with the carriers of this invention in carrying out this process. I have found the carbonyl compounds that are effective have a structural formula selected from the group consisting of wherein R is selected from the group consisting of hydrogen, alkyl, aryl and heterocyclic oxygen and sulfur radicals, and R and R" are selected from the group consisting of alkyl' and aryl radicals. Both the alkyl and the aryl radicals in R, R and R" may contain substituents such as alkoxy or hydroxy radicals. Table I'I sets forth the carbonyl compounds that have been used successfully in combination with the carriers of this invention.

TABLE II Aldehydes m-Hydroxy benzaldehyde p-Hydroxy benzaldehyde Piperonal o-Hydroxy benzaldehyde Veratraldehyde Benzaldehyde B-methoxy propionaldehyde Furfural Glyceraldehyde Anisaldehyde Salicylaldehyde propyl sultone Ethyl vanillin- 'Ihiophene-Z-aldehyde Patented Jan. 3, 1967 Ketones nation. Organic contamination may also be eliminated by circulating this pyrophosphate solution through activated carbon or other types of exchange or absorption media.

Although a number of combinations of carbonyl comacetophenone pounds can be used in connection with the carriers, as acetylacetone described previously, I find the combination of aldehyde, lsophorone particularly the furfural and his [sulfonaphthyl] methane dihydroxy acetone gives excellent results in reduction of roughness, increase In carrying out the process of this invention the optiof bnghgness a iz i denfslty mum operating conditions such as the pH, the temperaf at t Same tune O enng t 6 P058 1 lty o economl' ture, and the current density may vary depending upon ca f h f the bath composition and the object being plated. In genpougwmg egamples 0 6 F O t if g eral, good bright zinc deposits can be obtained only within 0 11 a 0 t g abtyglca pymp. ate a specific range of operating conditions. For example, p 3? bat avmg t e 0 owing aslc composition was when the pH is much above the desired range, the zinc use deposit loses its brightness, and when the pH is too low, Zn as Zn P O -XH O (31% Zn) g./liter 81 the current efiiciency decreases. Similarly, increasing the K 130: do 290 temperature reduces the brightness of the electrodeposit Total P. .O do 188 of zinc, but raises maximum current density that may be P O /Zu Weight ratio 7.5:1 used before roughness occurs. Increasing the temperature also decreases the cathode current efficiency. Table The pH of the bath was about 11 in all the cases and the III sets forth the range of the bath compositions and the temperature of the bath was maintained around 45 C. operation conditions suitable for the process of this invenw Plating operations in each example were carried out in tion. The preferred compositions and conditions also are an air agitated Hull test cell so the effect of a wide range stated. of current densities could be observed. The zinc deposit TABLE III in each example was plated on a Hull panel measuring 2 /2" x 3%" with l ampere current per panel for a period Range Preferred of 10 mmutes- The examples are used for the purpose of illustrating this invention and the synergistic eifect of the carrier in M t 10 tr (Hi0 W30 combination with the carbonyl compounds. In the ex- Pi vlzii veig iiiz %t atib. ?fi l ff:::III: eel-i011 7.0;1-5. 0-.1 amples Hun Panel was Plated first in the basic solution R E 05 3- 1 without the additives and then for each set of additives fii'f 'fig i fx' i: ":1 3 2, illustrated in the examples, two panels were plated, of g g el -5 which one was plated with the bath containing only one at Onyl ompmm additive and the second panel was plated in accordance with the process of this invention. The resultant panels Vigorous but uniform agitation of the plating bath, 40 were compared by visual examination of the zinc dewhich can be provided either by a mechanical or an air posits on the panels in both the high curient density agitator is desirable during the electrodeposition. The areas which were represented by one half of each Hull agitation permits the use of higher plating current densipanel, and the low current density areas, which were repties on the part being plated. resented by the remaining half of each panel. The back It is important during the plating operation that the coverage which indicates the throwing power of the panel metallic contamination should be eliminated to insure a also Was examined visually. The results are recorded in bright metallic deposit. Metallic contamination from for- Table IV which shows the synergistic elfects of various eign metallic ions such as cadmium, copper and lead is carbonyl compounds of the aldehyde and ketone types the most troublesome. Conventional purification methused in combination with a carrier, bis [snlfonaphthyl] ods should be used to eliminate such metallic contamimethane.

TABLE IV Additive Visual Inspection and Comparison Example Carbon Compound Carrier High Current Density Area Low Current Density Area Back Coverage 1. Coarse type of roughness; fine Coarse grained and dull; Poor, major portion of grained and semibri ht; uniform deposit. the back unplated. color of the deposit ark.

Roughness reduced; deposit Fine grained and semibright; Incomplete coverage. bright and metallic. color of the deposit dark; 2 m-hydroxy benzaldefreaky.

hyde 0.75 g./1iter.

Bis [sulfonaphthyl] Roughness reduced, deposit Smooth and bright deposit--- Excellent coverage.

methane 1.2 g./liter. bright and metallic.

Roughness reduced; hazy Deposit dull and non-uniform. Poor, major portion of bright deposit; non-uniform. the back unplated. 3 p-hydroxy benzaldehyde, 0.25 gJIiter. Bis [sulfonaphthyl] Deposit bright and metallic-.. Deposit bright and fine Excellent coverage.

methane 1.2 g./liter. grained; improved uniformity oi the deposit.

Roughness; hazy bright Fine grained; semibright;non- Incomplete coverage.

deposit. uniform. 4 Piperonal 0.25 g./1lter.

Bis [sulfonaphthyl] Deposit bright and metallic-.. Deposit bright and metallic; Excellent coverage.

methane 1.2 g./liter. uniform.

Roughness reduced; hazy Coarse grained dull deposit; Poor coverage. 5 O-hydroxy benzaldebright deposit;non-u.niform. non-uniform.

hyde 0.05 g./1iter.

Bis [snlionaphthyl] Roughness reduced; hazy Improved brightness and Excellent coverage.

methane 1.2 gJliter. brigfht detprosit; improved uniformity.

TAB LE IV Continued Additive Visual Inspection and Comparison Example Carbon Compound Carrier High Current Density Area Low Current Density Area Back Coverage Roughness; hazy bright Deposit bright and metallic; Incomplete coverage. 6 Veratraldehyde 0.1 deposit. skipping and freaky.

g. iter.

Bis [sulfonaphthyl] Deposit bright and metallic.-. Deposit bright and metallic--. Excellent coverage.

methane 1.2 g.[liter.

Roughness; hazy bright Fine grained, semibright Incomplete coverage. 7 Benzaldehyde 0.4 deposit; non-uniform. deposit; non-uniform.

g. ter.

Bis [sulfonaphthyl] Roughness; hazy bright Brightness improved Excellent coverage.

methane 1.2 g./liter. deposit.

Roughness; hazy bright Coarse grained, dull deposit; Incomplete coverage. 8 B-1nethoxy Propiondeposit; non-uniform. non-uniform.

aldehyde 0.6 g./liter.

Bis [sulionaphthyl] Roughness; hazy bright Improved in brightness and Excellent coverage.

methane 1.2 g./liter. deposit; non-uniform. uniformity.

Roughness reduced; fine Dull- Poor coverage.

grained, semibright deposit. 9 Furfural 0.1 g./liter Bis [sulfonaphthyl] Fine grained; semibright Fine grained; semibright Excellent coverage.

methane 1.2 g./liter. deposit. deposit.

Roughness, bright and metal- Fine grained, semibright Incomplete coverage.

lie deposit; skipping; nondeposit. 10 Glylritietraldehyde, 0.1 uniform.

g. er.

Bis [sulfonaphthyl] Roughness, bright and metal- Fine grained, semibright Excellent coverage.

methane 1.2 g./liter. lic deposit; skipping; nondeposit.

uniform.

Roughness, hazy bright Hazy bright deposit; non- Poor coverage. 11 Anisialldehyde, 0.6 deposit. uniform; skipping.

g. 'ter.

Bis [sulfonaphthyl] Roughness; deposit bright Deposit bright and metallic.-. Incomplete coverage.

methane 1.2 g./liter. and mettallic. 4

Roughness reduced; deposit Fine grained, semibright Incomplete coverage. 12 Salicylaldehyde bright and metallic. deposit, skipping; non- Pil'lopyl Sultoue, 0.05 uniform. g. 1 er.

Bis [sulfonaphthyl] Roughness reduced; deposit The brightness improved; Excellent coverage.

methane 1.2 g./1iter. bright and metallic. uniform.

Roughness; hazy bright Fine grained, semibright Incomplete coverage. 13 Ethi l lanillin, 0.4 deposit. deposit; non-uniform.

g. iter.

Bis [sulfonaphthyl] Roughness; hazy bright Improved in brightness Excellent coverage.

methane 1.2 g./liter. deposit.

Roughness; hazy bright Dull. Incomplete coverage.

deposit. 14 Thiophene-2-aldehyde 0.2 g./liter. Bis [sulfonaphthyl] Roughness; hazy bright Hazy bright deposit Excellent coverage.

methane 1.2 g.[liter. deposit.

Roughness reduced; hazy Fine grained. semibright Incomplete coverage.

bright deposit. deposit; color of the deposit 15 Acetylacetone 4 ml./ dark.

liter 5% solution.

Bis [suli'onaphthyl] Roughness reduced; hazy Deposit bright and metallic Excellent coverage.

methane 1.2 g./liter. bright deposit.

Similarly, the other carriers of this invention combine synergistically with a carbonyl compound of the aldehyde and ketone types to provide improvements in the brightness, uniformity and the low current density coverage of the electrodcpositcd zinc. Following are additional examples of the relative effects of these carriers on the zinc deposit when they are used alone or in combination with a carbonyl compound. The basic solutions and the operating conditions used in these examples are the same as those used in the previous examples.

Example 1 6 Two grams per liter of 8 amino, 1 naphthalene sulfonic :acid were dissolved in the basic pyrophosphate solution.

Zinc was electrodcpositcd onto a Hull panel. After the plating was completed, 0.1 gram per liter of furfural was added to the solution containing the carrier and a similar Hull panel was electrodeposited from this solution. These two plates were visually compared. It was found that the panel plated in accordance with the invention was brighter, more uniform and had better back coverage.

Examples 17-22 Similar to Example 16 except that 6,6'-imino bis-(1 naphthol-3) sulfonic acid; 2 naphthol-6,8 disulfonic acid;

2,6 naphthalene-disulfonic acid; 2,3- dihydroxy-6 naphthalene sulfonate (sodium salt); 1,5 dihydroxy naphthalene and 1,4 naphthalene diol were used separately as carriers in each example. When the two panels in each example were compared visually, the one plated in accordance with the process of this invention was either brighter, more uniform or had better back coverage.

Examples 23-26 Similar to the other examples except that 0.2 gram per liter of sodium allyl sulfonate was used as the carrier. The result was similar to those of the above examples.

From the examples given, the synergism between carriers of the type disclosed and carbonyl compounds, aldehydcs or ketones, in pyrophosphate plating solutions is made apparent by the improvement in the characteristics of the electrodepositcd zinc.

I claim:

1. The process for producing bright zinc deposits which comprises electroplating zinc from an aqueous alkaline pyrophosphate solution containing at least one zinc salt in which there is dissolved from about 0.5 to about 5.0 grams per liter of a carrier selected from the group consisting of (a) his [sulfonaphthyl] methane, (b) naphthalene derivates that contain substituents selected from the group consisting of sulfonic acids and their alkali metal salts, hydroxyl, amino and imino radicals, (c) benzene derivatives containing substituents selected from the group consisting of sulfonic acids and their salts with alkali metal and ammonium, alkyl and imino radicals, and (d) allyl sulfonic acid and its salts with alkali metals, and from about 0.025 to about 0.2 gram per liter of a carbonyl compound having a structural formula selected from the group consisting of wherein R is selected from the group consisting of hydrogen, alkyl, aryl and heterocyclic oxygen and sulfur radicals, and R and R" are selected from the group consisting of alkyl and aryl radicals.

2. The process for producing bright zinc deposits which comprises electrodepositing zinc from an aqueous alkaline pyrophosphate solution containing at least one zinc salt in which there is dissolved from about 0.5 to about 5.0 grams per liter of a carrier selected from the group consisting of (a) bis [sulfonaphthyl] methane, (b) naphthalene derivatives that contain substituents selected from the group consisting of sulfonic acids and their alkali metal salts, hydroxyl, amino and imino radicals, (c) benzene derivatives containing substituents selected from the group consisting of sulfonic acids and their salts with alkali metal and ammonium, alkyl and imino radicals, and (d) allyl sulfonic acid and its salts with alkali metals, and from about 0.025 and to about 0.2 gram per liter of an aldehyde having a structural formula wherein R is selected from the group consisting of hydrogen, alkyl, aryl and heterocyclic oxygen and sulfur radicals.

3. The process for producing bright zinc deposits which com-prises electrodepositing zinc from an aqueous alkaline pyrophosphate solution containing at least one zinc salt in which there is dissolved from about 0.5 to about 5.0 grams per liter of a carrier selected from the group consisting of (a) bis [sulfonaphthyl] methane, (-b) naphthalene derivatives that contain substituents selected from the \group consisting of sulfonie acids and their alkali metal salts, hydroxyl, amino and imino radicals, (c) benzene derivatives containing substituents selected from the group consisting of sulfonic acids and their salts with alkali metal and ammonium, alkyl and imino radicals, and (d) allyl sulfonic acid and its salts with alkali metals, and from about 0.025 to about 0.2 gram per liter of a ketone having a structural formula \O=O ,4 wherein R' and R" each is selected from the group consisting of alkyl and aryl radicals.

4. The process for producing bright zinc deposits which comprises electrodepositing zinc from an aqueous alkaline pyrophosphate solution containing at least one zinc salt in which there is dissolved from about 0.9 to 1.6 grams per liter of a carrier selected from the proup consisting of (a) his [sulfonaphthyl] methane, (b) naphcompound having a structural formula selected from the group consisting of wherein R is selected from the group consisting of hydrogen, alkyl, aryl and heterocyclic oxygen and sulfur radicals, and R and R are selected from the group consisting of alkyl and aryl radicals.

5. The process for producing bright zinc deposits which comprises electrodepositing zinc from an aqueous alkaline pyrophosphate solution .at a temperature ranging from about 40 C. to about 50 C., said solution containing 10 to 60 grams per liter of zinc which provides a pyrophosphate radical (P 0 to zinc weight ratio of 6.5 to 1 to 8.0 to 1 and a pH in the range from 10.5 to 12.0, in said solution there is dissolved from about 0.5 to about 5.0 grams per liter of a carrier selected from the group consisting of (a) his [sulfonaphthyl] methane, (b) naphthalene derivatives that contain substituents selected from the group consisting of sulfonic acids and their alkali metal salts, hydroxyl, amino, and imino radicals, (c) benzene derivatives contaninig substituents selected from the group consisting of sulfonic acids and their salts with alkali metal and ammonium, alkyl and imino radicals, and (d) allyl sulfonic acid and its salts with alkali metals, and fromabout 0.025 to about 0.2 gram per liter of a carbonyl compound having a structural formula selected from the group consisting of wherein R'is selected from the group consisting of hydrogen, alkyl, aryl and heterocyclic oxygen and sulfur radicals, and R and R are selected from the group consisting of alkyl and aryl radicals.

6. The process for producing bright zinc deposits which comprises electrodepositing zinc from an aqueous alkaline pyrophosphate solution at a temperature ranging from about 40 to. about 50 C., said solution containing 20 to 30 grams per liter of zinc which provides a pyrophosphate radical (P 0 to zinc weight ratio of 7.0 to 1 to 8.0 to 1 and a pH of about 11.0, in said solution there is dissolved from about 0.9 to about 1.6 grams per liter of a carrier selected from the group consisting of (a) his [sulfonaphthyl] methane, (b) naphthalene derivatives that contain substituents selected from the group consisting of sulfonic acids and their alkali.

metal salts, hydroxyl, amino, and imino radicals, (c)

benzene derivatives containing substituents selected from the group consisting of sulfonic acids and their salts with alkali metal and ammonium, alkyl and imino radicals,-

and (d) allyl sulfonic acid and its salts with alkali metals, and from about 0.05 to about 0.1 gram per liter of a carbonyl compound having a structural formula selected from the group consisting of gen, alkyl, aryl and heterocyclic oxygen and sulfur radicals, and R and R" are selected from the group consisting of alkyl and aryl radicals.

7. The process for producing bright zinc deposits which comprises electrodepositing zinc from an aqueous alkaline pyrophosphate solution at a temperature ranging from about 40 C. to about 50 C., said solution containing 10 to 60 grams per liter of zinc which provides a pyrophosphate radical (P to zinc weight ratio of 6.5 to 1 to 8.0 to 1 and a pH in the range from 10.5 to 12.0, in said solution there is dissolved from about 0.5 to about 5.0 grams per liter of bis [sulfonaphthyl] methane, and from about 0.025 to about 0.2 gram per liter of a ketone a structural formula o=o RI! wherein R and R each is selected from the group consisting of alkyl and aryl radicals.

8. The process for producing bright zinc deposits which comprises electrodeposi-ting zinc from an aqueous alkaline pyrophosphate solution at a temperature ranging from about 40 C. to about 50 C., said solution containing to 60 grams per liter of zinc which provides a pyrophosphate radical (P 0 to zinc weight ration of 6.5 to 1 to 8.0 -to 1 and a pH in the range from 10.5 to 12.0, in said solution there is dissolved from about 0.5 to about 5.0 grams per liter of his [sulfonaphthyl] methane, and from about 0.025 to about 0.2 gram per liter of an aldehyde having a structural formula wherein R is selected from the group consisting of hydrogen, alkyl, aryl and heterocyclic oxygen and sulfur radicals.

9. The process of claim 8 wherein about 0.9 to 1.6 grams per liter of said bis [sulfonaphthyl] methane is dissolved in said solution, and the concentration of said dissolved aldehyde is from 0.05 to 0.1 gram per liter.

10. The process of claim 9 werein the aldehyde is furfural aldehyde.

11. A bright zinc plating bath comprising an aqueous alkaline pyrophospha-te solution containing about 10 to 60 grams per liter of zinc which provides a pyrophosphate radical (P 0 to zinc Weight ratio of 6.5 to 1 to 8.0 to 1 and a pH in the range from 10.5 to 12.0, about 0.5 to about 5.0 grams per liter of a carrier selected from the group consisting of (a) bis [sulfonaphthyl] methane, (-b) naphthalene derivatives that contain substituents selected from the group consisting of sulfonic acids and their alkali metal salts, hydroxyl, amino and imino radicals, (c) benzene derivatives containing substituents selected from the group consisting of sulfonic acids and their salts with alkali metal and ammonium, alkyl and imino radicals, and (d) allyl sulfonic acid and its salts with alkali metals, and from about 0.025 to about 0.2 gram per liter of a carbonyl compound having a structural formula selected from the group consisting of R\ R C=O and cals, and R and R are selected from the group consisting of alkyl and aryl radicals.

12. A bright zinc plating bath comprising an aqueous alkaline pyrophosp'hate solution containing about 20 to 30 grams per liter of zinc which provides a pyrophosphate radical (P 0 to zinc weight ratio of from about 7.0 to 1 to 8.0 to 1, about 0.9 to 1.6 grams per liter of a carrier selected from the group consisting of (a) bis [sulfonaphthyl] methane, (b) naphthalene derivatives that contain substituents selected from the group consisting of sulfonic acids and their alkali metal salts, hydroxyl, amino, and imino radicals, (c) benzene derivatives containing substituents selected from the group consisting of sulfonic acids and their salts with alkali metal and ammonium, alkyl and imino radicals, and (d) allyl sulfonic acid and its salts with alkali metals, and about 0.05 to 0.1 gram per liter of a carbonyl compound selected from the group consisting of 0:0 and wherein R is selected from the group consisting of hydrogen, alkyl, aryl and heterocyclic oxygen and sulfur radicals, and R and R are selected from the group consisting of alkyl and aryl radicals.

13. A bright zinc plating bath comprising an aqueous alkaline pyrophosphate solution containing at least one zinc salt, about 0.5 to about 5.0 grams per liter of his [sulfonaphthyl] methane, and from about 0.025 to about 0.2 gram per liter of an aldehyde having a structural formula wherein R is selected from the group consisting of hydrogen, alkyl, aryl and heterocyclic oxygen and sulfur radicals.

14. A bright zinc plating bath comprising an aqueous alkaline pyrophosp'hate solution containing about 10 to 60 grams per liter of zinc which provides a pyrophosphate radical (P 0 to zinc weight ratio of from about 10.5 to about 12.0, about 0.5 to 5.0 grams per liter of bis [sulfonaphthyl] methane and about 0.025 to 0.2 gram per liter of an aldehyde having a structural formula of wherein R is selected from the group consisting of hydrogen, alkyl, aryl and heterocyclic oxygen and sulfur.

15. A bright zinc plating bath of claim 14 wherein said aldehyde is furfural aldehyde.

References Cited by the Examiner UNITED STATES PATENTS 2,101,581 12/1937 Henricks 20455 2,488,246 11/1949 Stareok et al. 204-55 2,529,700 l1/l950 Lowe et a1 20455 X 3,049,942 6/1962 Cox et al. 204-65 X 3,088,884 5/196'3 Passal 204--55 JOHN H. MACK, Primary Examiner.

G. KAPLAN, Assistant Examiner. 

1. THE PROCESS FOR PRODUCING BRIGHT ZINC DEPOSITS WHICH COMPRISES ELECTROPLATING ZINC FROM AN AQUEOUS ALKALINE PYROPHOSPHATE SOLUTIN CONTAINING AT LEAST ONE ZINC SALT IN WHICH THERE IS DISSOLVED FROM ABOUT 0.5 TO ABOUT 5.0 GRAMS PER LITER OF A CARRIER SELECTED FROM THE GROUP CONSISTING OF (A) BIS (SULFONAPHYTHYL) METHANE, (B) NAPHTHALENE DERIVATES THAT CONTAIN SUBSTITUENTS SELECTED FROM THE GROUP CONSISTING OF SULFONIC ACIDS AND THEIR ALKALI METAL SALTS, HYDROXYL, AMINO AND IMINO RADICALS, (C) BENZENE DERIVATIVES CONTAINING SUBSTITUENTS SELECTED FROM THE GROUP CONSISTING OF SULFONIC ACIDS AND THEIR SALTS WITH ALKALI METAL AND AMMONIUM, ALKYL AND IMINO RADICALS, AND (D) ALLYL SULFONIC ACID AND ITS SALTS WITH ALKALI METALS, AND FROM ABOUT 0.025 TO ABOUT 0.2 GRAM PER LITER OF A CARBONYL COMPOUND HAVING A STRUCTURAL FORMULA SELETECTED FROM THE GROUP CONSISTING OF 